.nav{ width:100%; height:auto; float:left; background:#fff;}
.nav li{ width:20%; height:70px; text-align:center; float:left; position: relative;}
.nav a{ color:#454545; width:100%; display:block; font-size:12px;  position: absolute; top: 50%; transform: translateY(-50%);}
.nav img{ width:35px;}
.nav span{ display:block; width:100%;}
